On Fri, 29 Apr 2022 at 20:01, Liam Howlett <liam.howlett@xxxxxxxxxx> wrote: > > * Christian Brauner <brauner@xxxxxxxxxx> [220429 08:05]: > > On Thu, Apr 28, 2022 at 10:41:27PM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: bdc61aad77fa Add linux-next specific files for 20220428 > > > git tree: linux-next > > > console output: https://syzkaller.appspot.com/x/log.txt?x=15bb3dc2f00000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=87767e89da13a759 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=2ee18845e89ae76342c5 > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1118a5f6f00000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=125bd212f00000 > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+2ee18845e89ae76342c5@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > ============================= > > > WARNING: suspicious RCU usage > > > 5.18.0-rc4-next-20220428-syzkaller #0 Not tainted > > > ----------------------------- > > > lib/maple_tree.c:844 suspicious rcu_dereference_check() usage! > > > > I _think_ for maple tree stuff you want to somehow ensure that > > Liam Howlett <liam.howlett@xxxxxxxxxx> > > gets Cced. > > Thanks for sending this along. Yes, it would be best if I was somehow > emailed for maple tree things. I did add myself to maintainers for this > file. Hi, Are you sure you want this persistently? And not biased by the fact that this code is just added? syzkaller does not blame anything in lib/*.c b/c the assumption is that for things like memcpy, atomic ops, vsprintf, xarray most bugs are really in the callers. If we start blaming lib/maple_tree.c then later ii will be your responsibility to reroute bugs when callers use if after freeing, etc to these callers. > > > other info that might help us debug this: > > > > > > > > > rcu_scheduler_active = 2, debug_locks = 1 > > > 5 locks held by syz-executor842/4211: > > > #0: ffff88807f0ae460 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x127/0x250 fs/read_write.c:644 > > > #1: ffff88801df04488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x28c/0x610 fs/kernfs/file.c:282 > > > #2: ffff8881453b9a00 (kn->active#106){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b0/0x610 fs/kernfs/file.c:283 > > > #3: ffffffff8bedc528 (ksm_thread_mutex){+.+.}-{3:3}, at: run_store+0xd1/0xa60 mm/ksm.c:2917 > > > #4: ffff88801e5e8fd8 (&mm->mmap_lock#2){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:117 [inline] > > > #4: ffff88801e5e8fd8 (&mm->mmap_lock#2){++++}-{3:3}, at: unmerge_and_remove_all_rmap_items mm/ksm.c:989 [inline] > > > #4: ffff88801e5e8fd8 (&mm->mmap_lock#2){++++}-{3:3}, at: run_store+0x2a5/0xa60 mm/ksm.c:2923 > > > > > > stack backtrace: > > > CPU: 0 PID: 4211 Comm: syz-executor842 Not tainted 5.18.0-rc4-next-20220428-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > Call Trace: > > > <TASK> > > > __dump_stack lib/dump_stack.c:88 [inline] > > > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > > > mas_root lib/maple_tree.c:844 [inline] > > > mas_start lib/maple_tree.c:1331 [inline] > > > mas_state_walk lib/maple_tree.c:3745 [inline] > > > mas_walk+0x45e/0x670 lib/maple_tree.c:4923 > > > mas_find+0x442/0xc90 lib/maple_tree.c:5861 > > > vma_find include/linux/mm.h:664 [inline] > > > vma_next include/linux/mm.h:673 [inline] > > > unmerge_and_remove_all_rmap_items mm/ksm.c:990 [inline] > > > run_store+0x2ed/0xa60 mm/ksm.c:2923 > > > kobj_attr_store+0x50/0x80 lib/kobject.c:824 > > > sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136 > > > kernfs_fop_write_iter+0x3f8/0x610 fs/kernfs/file.c:291 > > > call_write_iter include/linux/fs.h:2059 [inline] > > > new_sync_write+0x38a/0x560 fs/read_write.c:504 > > > vfs_write+0x7c0/0xac0 fs/read_write.c:591 > > > ksys_write+0x127/0x250 fs/read_write.c:644 > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > RIP: 0033:0x7f6a91306e79 > > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 > > > RSP: 002b:00007ffddeb8cde8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > > > RAX: ffffffffffffffda RBX: 00000000000f4240 RCX: 00007f6a91306e79 > > > RDX: 0000000000000002 RSI: 0000000020000000 RDI: 0000000000000003 > > > RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001 > > > R10: 0000000020117000 R11: 0000000000000246 R12: 000000000000cf84 > > > R13: 00007ffddeb8cdfc R14: 00007ffddeb8ce10 R15: 00007ffddeb8ce00 > > > </TASK>
